Process of producing tetra alkyl lead



Patented May 9, 1933 UNITED STATES PATEN T OFFICE ALFRED E. PARMELEE, OF CARNEYS POINT, NEW JERSEY, ASSIGNORS TO I. DU PONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE PROCESS OF PRODUCING TETRA ALKYL LEAD No Drawing.

tion by the reaction of ethyl halides with the sodium alloys of lead. These methods have consisted principally of low temperature, high vacuum distillation, steam distillation, and extraction with organic solvents. The

latter, however, is objectionable because the removal of the solvents is necessary, and this is diflicult and expensive. Also, vacuum distillation presents many difficulties and dangers. When steam distillation is employed it has been the practice to use low-pressure saturated steam, the temperature or which is approximately not above 1l0115 G. The literature on this subject discloses that tetra ethyl lead will decompose at tempera tures not much above 125 C.

An object of our invention is to overcome the difficulties heretofore experienced in the recovery of tetra ethyl lead from the metallic sludges inherently present in such processes. A further object of our invent-ion is to improve generally on the process of manufacturing tetra alkyl lead compounds. A particular object of our invention is to increase the yield of tetra alkyl lead. A further obiect of our invention is an improvement in the distillation of tetra alkyl lead from the sludges present. Other objects will appear hereinafter.

These objects are accomplished by the following invention in which we have found that tetra alkyl lead and particularly tetra ethyl lead. can be distilled from the sludges formed in the process of manufacture, with an increased completeness of removal as is indicated by increases in yield, provided that high temperature steam. and particularly steam superheated to temperatures between 200 C. and 300 (3., is employed in the step of distillation, instead of the ordinary saturated steam, and that tetra alkyl lead may also be recovered without decomposition if a mixture of the sludge and water is slowly Application filed March 28, 1931. Serial No. 526,126.

dropped into a still which is previously heated and maintained at a temperature approxi mately 200 to 300 C. Operating the process in this way results in a mixture'of tetra alkyl lialiii and water flash-distilling out of the s -1 y The following examples illustrate preferred embodiments of our invention, butit is to be understood taken as limitations thereof.

Emample l.'-A mixture of tetra ethyl lead and lead sludge such as is obtained by the interaction between leadmono-sodium alloy that these are not to be a and ethyl chloride is mixed with approximately 10 times its Weight of water. This mixture is then brought toa boil by the application of external heat by the use of a. steam jacket for large scale operation or on a small scale, by direct gas flame. When the mixture is boiling the external heat is removed and steam, superheated to 200-300 C. is introduced through orifices in the bottom of the still. Distillation by this procedure is generally complete in two to three hours. The tetra ethyl lead is recovered from the water fraction ofthe distillate in I the usual manner and the yield obtained will be approximately between three per cent and four per cent higher than it'would have been had ordinary saturated steam been employed. f

While we prefer the temperatures specified, these may be lower than 200 C. and even as high as 400 C. i

Emample Il.An iron still is provided with an oil bath or'other baths capable of being raised to 300 C. The temperature of the bath is elevated until theinternal temperature of the still reaches approximately 275 C. There'is then run into the still at such a rate that the, temperature does not fall below200 C. a mixture of one part of lead sludge containing tetra ethyl lead and ten parts of water. The tetraethyl lead and tained by the distillation of a like sample lead from metallic lead sludge which comwith ordinary saturated steam. prises distilling the mixture in the presence Similar improved results may be obtained of water at a temperature of from about 200 by flash-distilling in like manner other tetra C. to about 400 C. 5 alkyl lead compounds such as tetra methyl In testimony whereofxwe afiixour slgna- 70 lead and tetra butyl lead etc. tures. I o I As many apparently widely different em- MARION G. AMICK. bodiments of this invention may be made FREDERICK B. DOIVNING. without departing from the spirit thereof, ALFRED P M E- 10 it is to be understood that we do not limit ourselves to the foregoing examples or descriptions except as indicated in the following patent claims.

Vi e claim:

1. In the process of producing tetra alkyl lead by the interaction of alkyl halides and a lead sodium alloy. the step of removing the tetra alkyl lead from the metallic lead sludge present which comprises steam distilling the mixture with superheated steam heated to a temperature of from about 200 C. to about 400 C. 4

2. In the process of recovering tetra alkyl lead from metallic lead sludge which comprises contacting the mixture with superheated steam at a temperature of between 200 C. and 300 C.

3. In the process of recovering tetra ethyl lead from metallic lead sludge which comprises steam distilling the mixture with superheated steam at a temperature of between 200 C. and 300 C.

4. In the process of recovering tetra alkyl lead from metallic lead sludge which comprises fiash-distilling the mixture at a temperature of from about 200 C. to about 400 C.

5. In the process of recovering tetra ethyl lead from metallic lead sludge which comprises flash-distilling the mixture at a temperature of from about 200 C. to about 6. The process of recovering tetra alkyl lead from metallic lead sludge which comprises mixing the sludge with water, raising the temperature of a still to from 200 C. to 300 C. and gradually introducing the mixture of the sludge and water into the heated still while maintaining the still at such temperatures. 0

7. The process of recovering tetra ethyl lead from metallic lead sludge which comprlsesjmixing the sludge with water main- 65. taining the temperature of a still at approximately from 200 C. to 300 C. and gradually contacting the mixture of the sludge apill water with the heated surfaces of the s 1 v 8. The process of recovering tetra alkyl 0 125 lead from metallic lead sludge which comprises distilling the mixture in the presence of water at a temperature above that at which I the tetra alkyl lead will decompose in the a a absence of water at atmospheric pressure. no The, process of recovering. tetra alkyl I I 

